托福TPO23 Lecture1

TPO23 Lecture l- Archaeology (Antikythera (Mechanism) Narrator: Listen to part of a lecture in an archaeology class. Professor: I was talking to one of my colleagues in the physics department the other day, and we ended up discussing how one discovery can change everything. My colleague mentioned how the theory of relativity completely changed the field of physics. At any rates, that conversation got me thinking about archaeological finds that really changed our understanding of ancient civilizations. So I want to talk about the discovery of the Antikythera Mechanism. The Antikythera Mechanism was found a hundred years ago, under water in an ancient Greek shipwreck in the Mediterranean Sea. It was in extremely poor condition and in many corroded pieces. But once we figured out what it was and reconstructed it. Well, I simply don't have the words to convey how extraordinary this find was. The Antikythera Mechanism is a relatively small device, roughly the size of a shoebox, made of gears fitted inside a wooden case. In its original state, there were rotating dials and other indicators on the top, with letters and drawings showing the Sun, the phases of the moon and different constellations. Inside the box, bronze gears would have rotated the displays. The displays, uh, the indicators of the Antikythera Mechanism, would then moved to show the motion of the Sun and moon relative to the planets and stars. The device could be used to tell the different phases of the moon and much more. Well, scientists have recently analyzed the inscriptions on the mechanism and re-examine the other cargo in the ship wreck, and the evidence makes an absolute case that this device dates back to ancient Greece somewhere between 150 and 100 B.C.E. What makes that so fascinating is that before we found the Antikythera Mechanism, the earliest device we had that could track the Sun and moon like this was invented over 1,000 years later. So when this was first found, people literally would not believe it. Some of my colleagues insisted it had to have been made well after 100 B.C.E. But this physical evidence was conclusive. It was that old. Of course part of what made this find so unusual is that the Antikythera Mechanism is constructed of bronze. Now, it is not that bronze was all that rare in Greece then, it is just that bronze was valuable and could easily be recycled. It would have been relatively easy for a person with knowledge of metals to melt down bronze objects and forge them into ? well, say, coins. Bronze was used to made money back then. Or mold the bronze into anything else of value for that matter. We are very fortunate that the device ended up under water, because otherwise it probably would have ended up recycled into ? who knows what. Now, it was a challenge to figure out the Antikythera Mechanism. It spent over 2,000 years at the bottom of the sea before it was discovered. And even after it was discovered, it was still a number of years before we really understood what it was. You see, the mechanism had corroded underwater, and many of the gears were stuck together in a mass. Cleaning it was only partly successful. We could only get a good look at the structure of the gears after gamma-rays were used to see inside, very similar to the way X-rays are used to see your bones. Now, once we got a good look inside, we saw a really complex device. The many gears not only moved in a way that could indicate the phases of the moon. The Antikythera Mechanism also tracked both the lunar year and the solar year. Additionally, the gears also moved to match the motions of the planet and predicted eclipses. But one thing that is particularly notable is that the mechanism was so precise that it even took into account a particular irregularity in the moon's orbit, which requires some very complex math to replicate in mechanical device. You could say that the Antikythera Mechanism was a very precise calendar, which stands to reasons calendars were very important to ancient peoples. Religious festivals had to be held at the right time of year, crops needed to be planted at the right time as well. And let's not forget that eclipses in planetary motions had important symbolic meanings.